Explorers of brain development are still in the age of explosive discovery. New molecules expressed during neurogenesis are being found at an ever increasing rate, and asking how these molecules function together to specify pathways and targets will continue to be our most difficult question. How many different surface molecules contribute to neuronal pathfinding during development and what is the functional contribution that each makes to the dynamic abilities of embryonic neurons? We are beginning to answer these questions by using monoclonal antibodies to isolate new molecules expressed on developing neurons and glia in the grasshopper embryo, and by quantifying the dynamic behaviors and abilities of embryonic neurons using a high resolution time lapse video microscopy system. We are currently characterizing two new molecules, one has been cloned and the other protein has been partially sequenced, and intend to pursue six others with recently isolated monoclonal antibodies. Our goal is to combine these two approaches by developing a novel assay of cellular and molecular function in which we block the expression, or induce ectopic expression, of new molecules and observe differences in the dynamic behaviors of individual neurons in their normal environment.